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Questions and Answers
Which of the following statements accurately describes the role of macrophages in the spleen?
Which of the following cells are analogous to Kupffer cells in the liver, residing in the spleen and performing a similar function?
Which of the following statements accurately reflects the primary function of alveolar macrophages in the lungs?
Which of the following is NOT a characteristic of the process of phagocytosis?
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Which of the following statements accurately describes the response of macrophages to infection?
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Which of the following is NOT a characteristic of lymph nodes?
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Which of the following statements accurately describes the role of the lymphatic system in immune defense?
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Which of the following statements accurately describes the role of neutrophils in the inflammatory response?
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Which of the following statements accurately describes the role of bradykinin in the inflammatory response?
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Which of the following statements accurately describes the role of histamine in the inflammatory response?
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Study Notes
Inflammation and Defense
- Within minutes of inflammation, macrophages in tissues begin phagocytic actions and become mobile in response to chemotactic factors.
- Sessile macrophages break loose from their attachments and migrate to the inflamed area, contributing to the defense.
- Large numbers of neutrophils invade the inflamed area within the first hour, attracted by products in the tissue that cause chemotaxis.
Neutrophil Invasion
- The number of neutrophils increases by four-to fivefold within a few hours after the onset of severe acute inflammation.
- Neutrophilia is caused by inflammatory products that mobilize neutrophils from the bone marrow into the circulating blood.
Macrophage Invasion
- Monocytes from the blood enter the inflamed tissue and enlarge to become macrophages, providing a third line of defense.
- The buildup of macrophages in inflamed tissue is slower than that of neutrophils, but they become the dominant phagocytic cell after several days to several weeks.
Fourth Line of Defense
- The bone marrow greatly increases production of both granulocytes and monocytes, stimulated by granulocytic and monocytic progenitor cells.
- Myeloperoxidase, a lysosomal enzyme, catalyzes the reaction between H2O2 and chloride ions to form hypochlorite, which is exceedingly bactericidal.
Monocyte-Macrophage Cell System
- The reticuloendothelial system (monocyte-macrophage system) consists of monocytes, mobile macrophages, fixed tissue macrophages, and specialized endothelial cells in the bone marrow, spleen, and lymph nodes.
- Fixed tissue macrophages can break away from their attachments and become mobile macrophages when appropriately stimulated.
Tissue Macrophages
- Tissue macrophages in the skin and subcutaneous tissues (histiocytes) can divide in situ and form more macrophages when infection begins.
- Macrophages in lymph nodes trap foreign particles that enter the tissues, such as bacteria, in a meshwork of sinuses.
- The spleen is similar to lymph nodes, with blood flowing through the tissue spaces of the spleen and macrophages lining the trabecular meshwork of the red pulp and venous sinuses.
Inflammation
- Tissue injury releases multiple substances that cause secondary changes in the tissue, including increased local blood flow and capillary permeability.
- Inflammation causes "walling off" the area of injury from the remaining tissues, delaying the spread of bacteria or toxic products.
- The intensity of the inflammatory process is usually proportional to the degree of tissue injury.
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